After choosing a reference book, want to see the introductive share that delivers a letter first.
选择好一套参考书后，先要看一下书的前言部分。
2
Service category, such as consultative information service, competitive information and introductive contents etc.
服务类。包括参照性信息服务、竞技性信息和知识性内容等。
3
Chapter 5s are introductive is use the process in should notice of problem do to elaborate, be the customer should accept in register process of service item.